Various retinal analogs will be synthesized, irradiated with monochromatic light, and the various double bond isomers will be separated by high-speed liquid chromotograpy. After structure determination, the respective pure retinals will be tested for rhodopsin formation-with opsin. The synthetic retinals will be tailored so that collectively they will give a clearer definition of the steric and chiral criteria of the opsin binding site and cavity. A C14-labeled retinal derivative capable of affinity binding to nearby amino acid moieties of opsin through the very reactive carbene will be synthesized to acquire further information of the opsin cavity. The mechanism of the photochemical process of bleaching will be studied. We hope to gain additional information of the Schiff base linkage by laser Raman and Fourier transform ir measurements.